1. Field of the Invention
This invention relates to novel yarns for the manufacture of Saxony carpets, upholstery and other applications, carpets manufactured therefrom and the method of their manufacture. The yarns of the invention comprise untwisted wrapped singles yarns having a core strand and a wrapper yarn. The wrapper yarn is comprised of a base synthetic fiber and a heat-activated binder fiber with a melting point substantially below that of the base synthetic fiber. The Saxony carpets of the invention are comprised of untwisted singles yarn tufts and are possessed of surface appearance, individual tip retention, pile density, resilient hand and wear resistance comparable or superior to conventional Saxony carpets made from multiple plied twist set yarns.
2. Description of the Related Art
A large portion of carpets used in residences in the United States are known as cut pile carpets. In their manufacture, pile yarn is inserted into a backing material as loops. The loops are cut to form vertical tufts and then usually sheared to an even length. There are two principal types of cut pile carpets: plush and Saxony. In plush carpets, the fibers from one tuft are indistinguishable from the fibers from surrounding tufts, giving a velvet-like appearance. In Saxony carpets, the individual pile yarn tufts are well defined giving a pointilist effect.
Cut-pile carpet is customarily produced from staple yarns or bulked continuous filament yarn. Staple fiber may be processed into yarn suitable for cut pile carpets by techniques known in the art. Generally, such techniques involve first combing crimped staple fiber in a carding machine to form a sliver which is a continuous strand of loosely assembled fibers without twist. The sliver is then drafted on a drafting machine to improve its thickness uniformity and subsequently spun and twisted on a spinning machine to form singles twisted yarn.
To produce plush carpets, the singles twisted yarn may be tufted directly into the backing material. However, to produce Saxony carpets, the torque in the singles twisted yarn must be neutralized. This is done by plying with other singles twisted yarn(s) to form a 2-ply or 3-ply yarn construction and twisting the plied yarns in the opposite sense from the twist in the singles yarn. The twisted yarn is then subjected to a heat-setting operation where the twist is heat-set utilizing one of several commercially available twist setting processes such as the Suessen or Superba processes, thus making the yarn suitable for tufting.
In a typical twist setting process, the yarn is passed through a heated chamber, while in a relaxed condition. The temperature of this process step is crucial to the proper twist setting of the base fiber to obtain desired properties of the final carpet product. For nylon-6 base fiber, the conditions for this step are typically 190-200° C. with a residence time of about 60 seconds for the Suessen process and about 130-140° C. with a residence time of about 60 seconds for the Superba process.
Similarly, bulked (texturized or crimped) continuous filament nylon yarn is produced according to various conventional methods. Twisting, entangling, or direct cabling may be utilized in various processes. For example, a 2-ply twisted yarn combining 2 ends of 1185 denier 70 filament yarn is prepared and subjected to conventional twist setting conditions, such as that for the staple yarn above or in an autoclave at 132° C. in saturated steam with a residence time of about 60 minutes. Multiple ends of the twist set yarns are tufted into cut pile carpet and conventionally finished to obtain the desired Saxony carpet product.
The perceived value of Saxony carpets is dependent upon several factors including carpet bulk and carpet “texture retention.” By the term, “texture retention” as used herein, it is meant the ability of the carpet to retain its original tuft definition after being subjected to traffic. When Saxony carpets are new, they have a pleasing texture. The bulked yarns, which form the tufts, provide firmness and body to the carpet. The ply-twist in the individual tufts allows for good tuft definition, which gives the carpet a uniform and sharp appearance. Each tuft appears distinctly separate from neighboring tufts. However, when the carpet is subjected to a high degree of traffic, the tufts begin to untwist. This loss of twist causes the tuft tips to splay open. The individual filaments of one tuft tend to mingle with filaments of adjacent tufts giving the carpet a matted appearance and loss of texture. A need exists for yarns that improve texture retention in carpets.
It is known that carpet bulk can be improved by increasing the face weight of the carpet or by increasing the crimp imposed on the face fiber. However, carpet face weight is directly proportional to the carpet's total production cost. Furthermore, highly crimped staple fiber can create processing problems, especially during the carding operation. A need exists for Saxony carpet yarns that may be tufted into carpets to provide good carpet bulk in such a manner that the above problems are avoided.
It is known that conventional Saxony carpet yarns require two or three plies of twisted singles yarns re-twisted together in order to yield carpets having satisfactory bulk and texture retention. Thus far, it has not been possible to produce satisfactory Saxony carpets from singles yarns. However, the process of twisting, plying and re-twisting several singles yarns together is slow and costly. A need exists for a singles yarn construction, that when used without further plying, will yield Saxony carpet quality at least equal to that obtained from multiple plied twist set yarns, and which can be made by a simpler, more economic process.
There is a long history of prior art processes that have had the objectives of improving the properties of yarns for various purposes through use of a low melting binder material incorporated in the yarn. These include U.S. Pat. Nos. 2,880,112; 3,494,819; 3,494,822; 3,828,542; 3,877,214; 4,552,6034; 4,644,741; 5,910,361; European Patent Nos. 444,637; 696,655; British Patent No. 2,205,116; South African Patent No. 72,0545 (equivalent to French Patent No. 72,02930); and Japanese Patents and Publications Nos. 61-10023; 61-100222; 61-245322. More pertinent to the current invention are U.S. Pat. Nos. 2,252,999; 3,494,822; 4,668,552; 4,668,553; 4,871,604; 5,010,723; 5,141,780; 5,478,624; 5,567,256; PCT Publication Nos. WO 88/03969; WO 94/09196; WO 94/20657; European Patent 324,773, and Japanese Patents and Publications Nos. 52-18835; 60-224,831. Most pertinent, the current invention is an improvement of the co-pending application Ser. No. 08/933,822 filed Sep. 19, 1997, and South African Patent 98/8628.
U.S. Pat. No. 5,478,624 and European Patent 324,773 describe carpet yarns comprising a blend of at least one base fiber selected from the group consisting of polyester, nylon 6 and nylon 66, and 1-12 weight percent of a heat activated binder fiber. The disclosure of U.S. Pat. No. 5,478,624 is hereby specifically incorporated by reference to the extent not inconsistent herewith. U.S. Pat. No. 4,668,552 describes a wrapped yarn for upholstery fabrics comprising a body strand of untwisted staple fibers and a binder strand formed of about 3 to 10 wt. % of a thermoplastic polymer having heat shrinkable and fusible properties. Japanese Kokai 60-224,831 describes single ply twisted carpet face yarns for plush carpets. Co-pending application Ser. No. 08/933,822 filed Sep. 19, 1997 and South African Patent 98/8628 broadly describe wrapped yarns comprising a binder material in the wrapper yarns.
Each of the yarn constructions in the patents and publications cited above represented improvements in the state of their respective arts. However, none described the specific constructions of the yarns of this invention and none satisfied all of the needs met by this invention.